And I'm Steve Inskeep. Missouri Senate candidate Todd Akin was going to face trouble, no matter what. But it's Akin's fate that he also faces a deadline today.

GREENE: If he should withdraw from the U.S. Senate race by 5 o'clock Central Time this afternoon, it will be easy for party officials to name a replacement. And he is under pressure not to miss this opportunity.

INSKEEP: Akin was on TV explaining why he opposes abortion in cases of rape, when he spun out a theory about how he believed women rarely become pregnant after, quote, "legitimate rape." His claim, which is contrary to medical studies, prompted nationwide criticism; prompted him to apologize. But as of now, Akin says he will not quit. NPR's Brian Naylor begins our coverage.

BRIAN NAYLOR, BYLINE: Republicans have viewed the seat in Missouri - now held by Democrat Claire McCaskill - as one of their best chances for a pick-up. The party, and aligned outside groups, have been pouring money into the state - running millions of dollars in negative ads against her. But party leaders are telling Akin that if he stays in the race, the money spigot will be shut off. GOP Chairman Reince Priebus offered this not-so- subtle advice to Akin, on CNN last night.

REINCE PRIEBUS: If it was me, I would step aside and let someone else run for that office.

NAYLOR: Mitt Romney, though stopping short of saying Akin should withdraw, made it clear he wouldn't support him. Romney was interviewed on a New Hampshire TV station, with running mate Paul Ryan at his side.

MITT ROMNEY: He should understand that his words, with regards to rape, are not words that I can defend, that we can defend; or that we could defend him.

NAYLOR: Akin, a six-term congressman, has apologized for his comments, saying rape is, quote, "never legitimate." But appearing on Mike Huckabee's radio program, Akin said he would not withdraw.

REP. TODD AKIN: And I'm not a quitter. And my belief is, we're going to take this thing forward. And by the grace of God, we're going to - to win this - win this race.

NAYLOR: While the GOP establishment has lined up against him, Akin does have support from some social conservatives. The Family Research Council's Family ActionPac issued a statement saying it enthusiastically endorses Akin, calling him the victim of, quote, "gotcha politics."